Drawing table

ABSTRACT

A drawing table having a stand and a board linked to the stand in such a manner as to allow the board to be adjusted in position whereby the weight of the board creates a second moment about the axis opposing the first moment. A compensating means varies the second moment to compensate for variations in the first moment due to changes in the position of the board so that the board is balanced in any position.

United States Patent [191 Kuhlmann et al.

in] 3,826,204 July 30, 1974 DRAWING TABLE [75] Inventors: FranzKuhlmann; Arnold Gundlach; Horst Seiifert, all of Wilhelmshaven, Germany[73] Assignee: Franz Kuhlmann KG,

Wilhelmshaven, Germany [22] Filed: Oct. 11, 1972 [21] Appl. No.: 296,586

[52] U.S. Cl. 108/2, 108/4 [51] Int. Cl. A04f 5/12 [58] Field of Search108/1-10; 248/372 [56] References Cited UNlTED STATES PATENTS 1,859,4565/1932 Nestler 108/2 1,956,546 4/1934 Froelich 108/2 H I, I0 I] 110 29 ii l 10' 1 t l 2,710,780 6/1955 Lawes 108/2 2,982,050 5/1961 May 108/23,089,275 5/1963 Alabor 108/2 3,213,809 10/1965 Kntskc 108/2 3,359,92712/1967 Janus 103/2 Primary Examiner-Paul R. Gilliam Attorney, Agent, orFirm-Holman & Stern ABSTRACT 10 Claims, 3 Drawing Figures DRAWING TABLEBACKGROUND OF THE INVENTION The present invention relates to a drawingtable comprising a stand and a drawing board which is secured by meansof linkage means, pivotably journalled on the stand head, with theweight of the drawing board being counter-balanced in any position ofthe board.

PRIOR ART Drawing tables are known, in which the weight balancing actionis performed by springs or gas springs. With such drawing tables, theweight of the drawing 1 board inclusive of accessories such as adrafting machine, receptacle, etc., is determined precisely, and thespring or springs are selected accordingly. It is observed in practicehowever that the characteristic curves of the springs or gas springsincur differences which do not allow uniform weight balancing. Adifference may arise moreover in the weight of the drawing boards, ofthe drafting mechanism and/or other accessories, which may bycounteracted only be means of springs having a different rating. Theoperation of hooking and unhooking the springs is very difficult andonerous and can be performed by a trained operative only. In addition,the springs incur fatigue in the course of time, the characteristiccurve of a spring changes and weight balancing is thus inoperative. Forthis reason, the joints and brake of the drawing tables have been givena stiff action, so that a balance may be established by means of theadditional friction.

OBJECT AND SUMMARY OF THE INVENTION The present invention is intended toeliminate these shortcomings. It attempts to provide so precise a weightor counter balance, to provide an adaptation to change conditions of thedrawing board effective weight, in such an uncomplicated way that thedrawing table joints may be arranged to pivot freely.

According to the present invention, there is a drawing table comprisinga stand, a board, linkage means pivotably connecting the board to anaxis on the stand in a manner allowing the board to be adjusted inposition and whereby the weight of the board creates a fist moment aboutsaid axis, counterbalancing means creating a second moment about saidaxis opposing the first moment and means for varying the second momentto compensate for variations in the first moment due to changes inposition of the board so that the board is balanced in any positionthereof.

Preferably, the means for varying the second moment comprises means forvarying the point of application relative to said axis of a forcecreating the second moment.

Furthermore, the linkage means comprises a first arm pivotably attachedto said axis on the standand pivotably attached to the board, therebylinking the stand to the board; a second arm pivotably attached to saidaxis on the stand; and a link arm pivotably attached to the board andsaid second arm.

Also the counterbalancing means may be a helical spring attached at oneend to the stand and at another end to a correct member rotatable aboutsaid axis upon movement of the board.

The point of action of the spring is adjustable or displaceable. Due tothis displaceability, it is possible to take up tolerances in a simplemanner and to allow so precise an adjustment that the bearing points ofthe parallelogram linkage means, in particular the bearing in the standhead, may be equipped with needle roller or ball bearings, so that thedrawing table may be moved without effort in the unbraked state. Thistable may accordingly also be used by female drafting personnel whileworking in the seated position.

A complementary adjustment means is provided according to the presentinvention, by the fact that the free extremity of the balancing helicalspring is hooked to an eyebolt which is adjustably arranged on the standfor varying the tension of the balancing spring. In conjunction with thepossibility of displacing the point of action, which results in a changeof the moment applied by means of the spring, adjustments may be madewithin wide limits, so that, the inclusion of complementary accessorieson the drawing board may also be considered without impairing the freedisplaceability of the drawing table in the unbraked state.

A preferred embodiment of the invention is characterized in that a pivotspindle to which the first or upper rocking arm is firmly connected, hasfastened thereto a disc-shaped receiving element for a corrector discrotatable around the axis of the pivot spindle, of which the outer rimextends spirally and has a receiving groove for a cable connected to thebalance spring. The lever arm with which the balancing spring acts withrespect to the pivot spindle axis is varied by turning the correctordisc with respect to the receiving element due to the spiral form of thecorrector disc. The opposing moment engendered by the helical spring isvaried thereby.

The corrector disc is concomitantly and preferably constructed as apartial disc and comprises a swivellably secured screwbolt carrying athrust element adjustable by means of a nut, and held in a rotatablemanner in a transversely directed recess of the receiving element. Thedisplacement of the corrector disc with respect to the receiving elementis thus performed by turning the nut on the screwbolt, a sticking orjamming action during the displacement being prevented by virtue of therotatable arrangement of the thrust element in the recess of thereceiving element.

To secure the cable fastened to the balancing spring in non-jammingmanner and according to a further embodiment of the invention, thecorrector disc has a recess arranged transversely to the receivinggroove at the extremity of the latter on its extremity bearing thescrewbolt, with a securing element for the cable of the balancing springbeing held rotatably in said recess. The securing element concomitantlyextends transversely to the disc and bears against a collet situated onthe extremity of the cable.

Due to the spirally shaped form of the periphery of the corrector disc,which is coupled to the pivot spindle through the receiving element andis thus entrained in rotation in case of a pivotal displacement of therocking arm during the displacement of the drawing board, the momentapplied by the spring with respect to the pivot spindle axis undergoesan adaptation to the position of the drawing board changed with respectto the pivot spindle axis. A precise weight balancing action is thusassured in all positions of the board.

According to a further embodiment of the invention, the parallelogramlink may be connected to an adjustable lever which is acted upon- .by atleast one other spring which has its other extremity secured to a springmounting which is displaceable in the vertical and horizontal direction.This spring equally serves the purpose of balancing, and the adjustmentmay be made either on the lever or the spring mounting. This adjustmentserves the purpose of adaptation to the different tilted positions ofthe drawing board.

In further development of the invention, the weight balancing system issituated within the stand which is hollow. Accordingly, no linkageprojects behind the stand, and a considerable saving of space isaccomplished thereby.

To permit equalization between the different center of gravity positionsresulting from the incorporation of a carriage drafting mechanism inplace of a parallelogram drafting mechanism, and according to a furtherembodiment of the invention, the drawing board is arranged to bedisplaceable with respect to a securing or supporting bar acted upon bythe pivoting linkage arms. In conjunction with the already definedbalancing system, this arrangement renders it possible to employcarriage drafting mechanisms as well as parallelogram draftingmechanisms on the drawing table, without having to perform a replacementof the springs of the balancing system.

A particular embodiment will now be described, by way of example, withreference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially sectioned frontview of a drawing table without a board,

FIG. 2 is a section along the line II--II of FIG. 1, the view looking inthe direction of the arrows, and

FIG. 3 is a section along the line III-III of FIG. 1, the view lookingin the direction of the arrows.

DETAILED DESCRIPTION OF THE DRAWINGS A pivot spindle 2 constructed as ahollow spindle is arranged in freely rotatable manner by means of needleroller bearings 3 in the upper portion of a stand or pedestal 1consisting of two pedestal feet. Upper pivot or rocking arms 4 arefirmly coupled to the pivot spindle 2, for example by being castintegral therewith.

The pivot spindle 2 has a continuous tube 6, a partial tube 5a extendingwithin a brake situated on the stand or pedestal head in each case, anda covering tube 5b situated between the brakes. The tubes 5a and 5b arefirmly joined to the continuous tube 6 by means of a rivet 7.

Only the arrangement on the left-hand side pedestal column 1 isdescribed in the following, since the righthand side column issymmetrical and identical thereto. A receiving element 8 is fastened bymeans of a grub screw 9 to extremity 6a of the tube 6. Between the upperpivot arm 4 and the needle roller bearing 3 is situated another rockingarm 10 which is firmly joined to a bearing tube 10a by integral casting,with the bearing tube 10a being pivotably arranged within the brakingsystem and rotatable on the tube 6. The arms 4 and 10 compriseentraining pins 4a for braking plates 11 and 12 of the braking system.Between the two rocking arms 4 and 10 are situated plate springs 13which bear directly onto the tube 6 and have the purpose of separatingthe braking plates 11 and 12 from each other when the brake is released.Accordingly, the plate springs 13 bear against the partial tube 5aconnected to the rocking arm 4 and against the bearing tube 10aconnected to the rocking arm 10. A bolt 14 which secures intermediatebraking plates 11a and 12b is firmly inserted into a pedestal head la.

A parallelogram link arm 15 is pivotably journalled on the rocking arm10 and is joint-coupled to a securing bar 17. The bearing bolts employedfor the articulation joints are marked 19. A drawing board 18 isfastened to the securing bar 17 on which the upper rocking arm 4 isjointedly secured by means of bearing bolts 19 and together with therocking arm 10 and the parallelogram link arm 15 forms a movableparallelogram. Fastening is performed by means of screws 20 passingthrough longitudinal slots 17a of the securing bar 17 and thus allowingfor the displacement of the drawing board 18 with respect to thesecuring bar. This displacement of the drawing board in the slots of thesecuring bar is required for adjustment of the weight balancing actionby displacement of the center of gravity, which remains to be describedin detail.

The parallelogram link 15 is connected to a lever 16 which isdisplaceable with respect to the arm 15. The lever 16 is acted upon bytwo springs 21 whose other extremities are hooked into a springsuspension system 22 which is held on the pedestal head la in verticallyas well as horizontally displaceable manner. Together with ano herspring whose incorporation remains to be described, the springs 21 servethe purpose of weight balancing.

The receiving element 8 has a groove 8a extending concentrically to thepivot axis of the pivot spindle 2 and receiving a corrector disc 23which engages with an appropriate projection 23a in the groove 8a. Thecorrector disc 23 is constructed as a partial disc in the form of anannular sector and at it extremity which is that situated at the top inthe assembled state, has a screwbolt 25 which is jointedly fastened onthe corrector-disc 23 by means of a fork element 25a and a bolt 26. Thescrewbolt 25 traverses a thrust element 24 which is borne in a recess 8bof the receiving element 8. A nut 27 which bears on the thrust element24 is operated on the screwbolt 25 to adjust the corrector disc 23 withrespect to the receiving element 8.

As apparent from FIGS. 1 and 3, the corrector disc 23 is equipped with areception groove 23a for a cable 29 which is connected to a tensionspring 32. The cable 29 is immobilized on the upper extremity of thecorrector disc by means of a cylindrical securing element 28, with thesecuring element 28 concomitantly being held rotatably in acorresponding recess 23b extending transversely to the receiving groove23a. The securing element 28 then bears on a collet 31 joined firmly tothe cable 29. A suspension loop in which is hooked the balance spring32, is formed by means of a clamping sleeve 30 at the other extremity ofthe cable.

The other extremity of the balancing spring 32 is hooked into an eyebolt33 which is inserted into a bracket 34 of the pedestal 1 and secured bymeans of a nut 35 employed to adjust the tension of the spring. 36 marksa sealing flap giving access to the adjusting nut 35 within the hollowpedestal 1, wherein the balancing springs are housed.

The external edge of the corrector disc 23, meaning the bottom of thereception groove 23a, is spirally formed so that the point of action ofthe balancing spring 32 varies with respect to the pivot axis duringrotation of the corrector disc with respect to the pivot axis.

The table weight balancing operation is performed by fine adjustmentthroughout the course of the displacement, by means of the correctordisc 23. The tension of the balancing spring 32 is varied by means ofthe nut 35, if additional equipment is installed in the system. Thetilting movement applied through the parallelogram link and the lever 16is performed by displacement of the lever 16, or at the bracket 34.Since this displacement has a secondary importance in the balancingaction, the springs 21 normally do not require adjustment. The optionalincorporation of a carriage or parallelogram drafting mechanism on thedrawing board may be taken into account by displacement of the drawingboard 18 in the longitudinal slots 17a of the securing bar 17 and byvarying the spring tension of the balancing spring 32, so that thecompensation system may be employed for carriage as well asparallelogram drafting mechanisms, without conversion.

We claim.

j 1. A drawing table including a stand, a board, a horizontal spindleconstituting an axis rotatably mounted in the stand, a first arm mountedon the spindle adjacent each end thereof, a second arm pivotally mountedon the spindle adjacent each end thereof, each of said first arms beingpivotally attached to said board, a link arm pivotally attached to eachof said second arms and to said board, a compensating member having aperipheral spiral groove rotatably mounted adjacent each end of saidspindle, a cable having first and second ends, said cable being attachedat the first end to the compensating member and located in the spiralgroove, a counterbalancing means adjustably connected to the stand, andthe second end of the cable being attached to the counterbalancingmeans, the attachment of the cable to the compensating member in thespiral groove enabling the point of action of the counterbalancing meansto vary with respect to the pivot axis during rotation of thecompensating member with respect to the pivot axis, the arrangementbeing such that the first and second arms and the link arms connectingthe board to the horizontal spindle allow the board to be adjusted inposition and in which the weight of the board creates a first momentabout the axis and the counterbalancing means creates a second momentabout the axis, with said compensating member varying the second momentto compensate for variations in the first moment due to changes in theposition of the board whereby the board is balanced in any positionthereof. 7

2. The drawing table as claimed in claim 1 in which the counterbalancingmeans is a helical spring.

3. The drawing table as claimed in claim 2 in which the adjustableconnection of the counterbalancing means to the stand includes aneyebolt to which the helical spring is attached, a bracket on the standreceiving the eyebolt, and an adjustment nut for the eyebolt foradjusting the position of the eyebolt on the bracket for varying thetension of the helical spring.

4. The drawing table of claim 1 further comprising a receiving discfixed to said first arm and rotatable about said axis, the receivingdisc being linked to the compensating member having a peripheral spiralgroove for varying said point of application.

5. The drawing table of claim 4 wherein the compensating member is apartial disc sector.

6. The drawing table of claim 5 wherein the compensating member has apivotably secured screwbolt carrying a thrust element which isadjustable by means of a nut on the screwbolt and rotatably secured inatransversely directed recess of the receiving disc.

7. The drawing table of claim 6 wherein the compensating member has arecess situated in the sides of the spiral helical groove of thecorrector member and extending transversely to the spiral helical grooveadjacent the screwbolt, a securing element for the cable of the helicalspring being rotatably secured in said recess.

8. The drawing table of claim 7 wherein the link arm is connected to anadjustable lever acted upon by a second spring which is secured on aspring mounting of the stand, the spring mounting being adjustable invertical and horizontal directions.

9. The drawing table of claim 8 wherein the helical spring, cable, andcompensating member are housed within the stand.

10. The drawing table of claim 9 wherein the drawing board isdisplaceably arranged on a securing bar which is pivotably fixed to saidfirst arm and said link arm.

1. A drawing table including a stand, a board, a horizontal spindleconstituting an axis rotatably mounted in the stand, a first arm mountedon the spindle adjacent each end thereof, a second arm pivotally mountedon the spindle adjacent each end thereof, each of said first arms beingpivotally attached to said board, a link arm pivotally attached to eachof saId second arms and to said board, a compensating member having aperipheral spiral groove rotatably mounted adjacent each end of saidspindle, a cable having first and second ends, said cable being attachedat the first end to the compensating member and located in the spiralgroove, a counterbalancing means adjustably connected to the stand, andthe second end of the cable being attached to the counterbalancingmeans, the attachment of the cable to the compensating member in thespiral groove enabling the point of action of the counterbalancing meansto vary with respect to the pivot axis during rotation of thecompensating member with respect to the pivot axis, the arrangementbeing such that the first and second arms and the link arms connectingthe board to the horizontal spindle allow the board to be adjusted inposition and in which the weight of the board creates a first momentabout the axis and the counterbalancing means creates a second momentabout the axis, with said compensating member varying the second momentto compensate for variations in the first moment due to changes in theposition of the board whereby the board is balanced in any positionthereof.
 2. The drawing table as claimed in claim 1 in which thecounterbalancing means is a helical spring.
 3. The drawing table asclaimed in claim 2 in which the adjustable connection of thecounterbalancing means to the stand includes an eyebolt to which thehelical spring is attached, a bracket on the stand receiving theeyebolt, and an adjustment nut for the eyebolt for adjusting theposition of the eyebolt on the bracket for varying the tension of thehelical spring.
 4. The drawing table of claim 1 further comprising areceiving disc fixed to said first arm and rotatable about said axis,the receiving disc being linked to the compensating member having aperipheral spiral groove for varying said point of application.
 5. Thedrawing table of claim 4 wherein the compensating member is a partialdisc sector.
 6. The drawing table of claim 5 wherein the compensatingmember has a pivotably secured screwbolt carrying a thrust element whichis adjustable by means of a nut on the screwbolt and rotatably securedin a transversely directed recess of the receiving disc.
 7. The drawingtable of claim 6 wherein the compensating member has a recess situatedin the sides of the spiral helical groove of the corrector member andextending transversely to the spiral helical groove adjacent thescrewbolt, a securing element for the cable of the helical spring beingrotatably secured in said recess.
 8. The drawing table of claim 7wherein the link arm is connected to an adjustable lever acted upon by asecond spring which is secured on a spring mounting of the stand, thespring mounting being adjustable in vertical and horizontal directions.9. The drawing table of claim 8 wherein the helical spring, cable, andcompensating member are housed within the stand.
 10. The drawing tableof claim 9 wherein the drawing board is displaceably arranged on asecuring bar which is pivotably fixed to said first arm and said linkarm.